This invention relates to the field of electrical connectors and switches, particularly those intended for infrequent switching functions.
In the broad field of telecommunications there is frequently a need for switching functions which are very reliable but which may be exercised only a few times during the life of the equipment. In telephone repeaters, for example, the amount of gain and equalization applied by the repeater is a function of the length of line between repeaters, a very wide range of adjustment being needed. Continuously variable components are very expensive, and the stocking of several types of repeaters with different amounts of gain and equalization is very cumbersome. The option type switch, therefore, by means of which increments of impedance may be connected in or out of the circuit to vary gain and equalization has proved very useful.
One type option switch which has been used in large quantities is a screw block terminal in which a metal screw is turned into a plastic threaded nut until the head of the screw makes contact with two terminals partially imbedded in the plastic nut to interconnect the two terminals. One difficulty with this screw block terminal has been caused by the lack of a positive snap action feel to the switching operation. The craftsperson turning the screw to provide the jumper connection cannot easily tell when the connection has been made secure enough for the necessary long term reliability. The tendency is to tighten the screw too tight, stripping the threads in the plastic nut; the terminal is thereby destroyed, requiring replacement. An object of this invention, therefore, is a reliable option switch with snap action.
A second problem with the screw block terminal was the inability to visually determine which of the screws were tightened enough to make connections and which were not. A second object of this invention, therefore, is an option switch with a visual indication of the option chosen.
Another type switch frequently used to provide the option switch function is the slide switch. Existing slide switches, however, are relatively expensive and relatively large compared to the miniaturized circuits of recent design. A third object of this invention, therefore, is an inexpensive miniature option switch assembly.
An inexpensive arrangement for the option switch function is the combination of a socket housing many female terminals and one or more jumper plugs which can be inserted in various positions in the socket to interconnect combinations of terminals. This type arrangement, however, raises the possibility that the plug can be inserted in such a way as to cross-connect circuits. A fourth object of this invention, therefore, is a socket and jumper plug option switch arrangement in which cross-connections are prevented. Finally, in a multi-terminal socket-jumper plug arrangement, the number of plugs in use may differ according to the particular option chosen. It is, therefore, very useful to have on hand in each piece of equipment the total number of plugs that might be used. It is a fifth object of this invention to provide storage for idle jumper plugs.